Substantial difficulty has heretofore been encountered in providing a sealed electrical connection between a motor lead extension cable and other types of power cables. Particular difficulty has also arisen in maintaining a durable electrical connector that is resistant to the harsh down hole environments often responsible for causing electrical failures between surface power sources and down hole equipment, such as electrical submersible pumps.
An electrical submersible pump, or ESP, provides artificial lift essential to increasing the flow of fluid to the surface of a production oil well. An electrical submersible pump is a pump with a hermetically sealed motor coupled to the pump body. Typically, the electrical submersible pump assembly is submerged in the fluid being pumped and requires a special power cable known as a motor lead extension cable, or MLE, for supplying power. The motor lead extension cable usually attaches to a pothead flange, which will mechanically fasten to the pump's motor.
Electrical power from the surface is typically brought from a remote source into the well through a wellhead barrier via a power cable. Inside the well another power cable, known as a main power cable, extends from the wellhead penetrator to the down hole electrical submersible pump. The motor lead extension cable connects with the main power cable and extends further down hole adjacent to the electrical submersible pump to the pump's power receptacle.
In currently known applications, the upper end of the motor lead extension cable is spliced to the main power cable. The lower end of the motor lead extension cable, fitted with a pothead flange, is plugged into the pump's power receptacle and mechanically affixed using cap screws.
In currently known applications, main power cables and motor lead extension cables typically include three conductive wires housed within various protective materials such as armored cladding, insulation or jacketing. The problem, however, with conventional main cables and motor lead extension cables is that very harsh down hole conditions, such as high hydrogen sulfide and high temperature environments, cause the cable's protective housings to breakdown, often causing electrical failure.
To protect against harsh down hole conditions, motor lead extension cables are typically surrounded with protective tubing. That is, each of the three conductive wires of the motor lead extension cable are encapsulated in an individual protective tube. The tube is typically constructed of stainless steel or metal alloy, which protects the conductive wires and prevents them from coming in contact with well fluids.
The protective tubing on the motor lead extension cables is typically limited to approximately 200 feet in length. With the operating depth of electrical submersible pumps normally greater than 4,000 feet, motor lead extension cables often need to be connected directly or indirectly to the main power cable in order to connect the electrical submersible pump with the surface power source.
Presently, drilling operators typically employ a tape wrap splice to connect down hole equipment with surface power, which involves crimping the conductive wires of two adjacent power cables together with an electrical crimp and then wrapping the crimp and a portion of each cable with nonconductive electrical tape. That is, each of the individual three phase conductor wires of the motor lead extension cable are typically crimped to the respective three phase conductor wires of the main power cable and wrapped with nonconductive adhesive materials for protection. Significant problems with the tape wrap splice connection include the lack of durability of the nonconductive tape and the connectors inability to hold up under corrosive conditions in the well. Such splice, connections therefore, are not always reliable and often fail, resulting in a delay or a total drilling stoppage at substantial expense to the operator.
The present invention overcomes the problems of the tape wrap spice by providing durable field attachable electrical connector that is resistant to harsh environments and not subject to breakdown. Embodiments of the present invention also overcome the aforementioned problems by providing a reusable and/or permanent connector. Further embodiments of the present invention provide a sealed connector that is completely impervious to well fluids.